Turbine engines may be used as a primary power source, such as in aircraft, or as a secondary, or auxiliary, power source to drive air compressors, hydraulic pumps, industrial gas turbine (IGT) power generators, or the like. In addition, turbine engines may be used as a stationary power supply, such as in a backup electrical generator for hospitals, and the like.
In a typical gas turbine engine, compressed air is generated by an axial and/or a radial compressor, and subsequently mixed with fuel and ignited. As a result, high velocity combustion gases are generated and directed against a plurality of stationary turbine vanes in the turbine engine. The stationary turbine vanes direct the high velocity gas flow to impinge on a plurality of turbine blades mounted on a rotatable turbine disk. The force of the impinging high velocity gas causes the rotatable turbine disk to spin at a high speed and thus generate power. In jet propulsion engines, the power created by the rotating turbine disk is used to draw more air into the engine and the high velocity combustion gas is passed out of the gas turbine aft end to create forward thrust. Other engines use the generated power to turn one or more propellers, fans, electrical generators, or other devices.
Engineers have progressively pushed turbine engines to extreme operating conditions in an attempt to increase the efficiency and performance of the turbine engines. Extreme operating conditions, such as high temperature and high pressure conditions are known to place increased demands on engine components, manufacturing technologies, and new materials used in the turbine engines. Increased strength and durability of some of these new materials has led to a gradual improvement in turbine engine design, but with these changes in engine materials, there has arisen a corresponding need to develop new repair methods appropriate for such materials.
Through normal service, there arises a need to repair turbine engine components such as turbine impellers and blisks. With respect to blisks, blade leading edge damage is fairly common, since the leading edge may be subject to foreign object damage or erosion after a period of service time. A significant savings can be realized if the damaged blades can be repaired and returned to service in lieu of blade replacement. Historically, the repair has been accomplished by machining away the damaged portion of the blades. Welding material was then manually deposited over the areas that had been machined away. The component was then mechanically machined by referencing a nominal model geometry in an attempt to reproduce the originally designed dimensions. Next, the component was hand finished by manually machining in order to place the component in a serviceable condition.
However, there are shortcomings associated with this historical repair method. The method may require leaving a significant amount of remaining material after mechanical machining, which must then be removed by a hand finishing process. The manual nature of the hand finishing process can be expensive and laborious and may thus result in an increase in the cost and processing time of the repair. The method may also result in significant scrap material. Thus, a need exists for the development of improved machining and weld repairing methods.
Accordingly, it is desirable to provide an improved method of repairing degraded gas turbine engine components. In addition, it is desirable to provide a repair method that can restore the approximate geometry, dimension and desired properties of the degraded gas turbine engine components. Finally, it is desired to provide a repair method that is less costly as compared to the alternative of replacing worn parts with new ones. The present invention addresses one or more of these needs.